For a number of years I have used Outlook as my mail client but it is so awful I have been searching for a viable alternative. Having tried Mailspring I really like it but now have the problem of trying to connect to my mail archive, which is held on my local SYnology NAS drive, but connected via a local IP address. If I try to add the account in Mailspring, it requests an email address but doesn’t offer the IMAP server connection options I would normally expect to find. Does anyone have any suggestions as to how best to proceed?
You can do this. The first screen only asks for an email address; the server fields are on the next screen. Choose IMAP / SMTP as the provider, enter your name, the address you use on the NAS mail server, and its password, and click Continue. The following page has separate Incoming (IMAP) and Outgoing (SMTP) sections where the Server field accepts a plain LAN IP like 192.168.1.20 (or a hostname), along with port, security, and username.
Two small gotchas: the address on the first screen has to look like something@host.tld (it’s just used as your identity / From address, it doesn’t need to resolve on the internet), and if the NAS uses a self-signed certificate tick “Allow insecure SSL” under the IMAP and SMTP sections, or pick “None” for security if the server is plain-text on the LAN. Mailspring also needs the SMTP half to succeed during setup, so point it at the NAS’s SMTP service (Synology Mail Server provides one) or any other SMTP server you have.